Image correction due to deformation of components of a viewing device

ABSTRACT

A display assembly displays a virtual object in a select location wherein an eye viewing the virtual object has an expected gaze direction. Deformation of the display assembly is detected. The deformation causes the virtual object to be viewable in an altered location wherein the eye has altered gaze direction. The virtual object may be displayed in a corrected location wherein the eye viewing the virtual object in the correct location has a corrected gaze direction that is moved closer to the expected gaze direction than the altered gaze direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 62/643,672, filed on Mar. 15, 2018, all of which isincorporated herein by reference in its/their entirety.

BACKGROUND OF THE INVENTION 1). Field of the Invention

This invention relates generally to a viewing device and to a method ofdisplaying rendered content, and more specifically to detecting andcorrecting for deformation of components of the view device.

2). Discussion of Related Art

Viewing devices that provide a rendered image have become popular forcomputing, entertainment and other purposes. A viewing device is usuallya wearable device with a display for rendering the image and may includevarious features such as the ability to have the user see athree-dimensional image, to have the user see a rendering within a realworld environment with or without fixing its location within the realworld environment, and displaying video or other moving renderings tothe user.

A viewing device has various components that deform over time due to itsuse. When these components deform, a virtual object that is rendered maynot be in its original location when the viewing device was still new.For example, a background application may display a virtual object in afixed location relative to the viewing device or in a fixed locationrelative to real world objects surrounding the user. In some instances,the viewing device may have a see-through display so that the user cansee the real world objects and the perceive the rendered objects in afixed location relative to the real world objects. The user may, forexample, perceive a rendered coffee mug on a real world table. When thecomponents of the viewing device deform, the coffee mug may not berendered on the table anymore, but instead float at some distance abovethe table. The coffee mug is thus not displayed to the user in a mannerthat is true to reality. In addition, if the coffee mug is used as aninterface element for the user to interact with the backgroundapplication, there may be a mismatch between where the backgroundapplication expects the coffee mug to be and where the user interactswith the coffee mug.

SUMMARY OF THE INVENTION

The invention provides a viewing device for displaying rendered contentincluding a display assembly configured to display a virtual object in aselect location on the display assembly, wherein an eye viewing thevirtual object has an expected gaze direction; and a deformationdetection system connected to the display assembly and configured todetect a measured gaze direction of the eye viewing the virtual objecton the display assembly and calculate a deformation of the displayassembly based on the measured gaze direction being an altered gazedirection that is different from the expected gaze direction.

The invention also provides a method of displaying rendered contentincluding displaying, with a display assembly, a virtual object in aselect location on the display assembly wherein an eye viewing thevirtual object has an expected gaze direction and detecting adeformation of the display assembly, wherein the deformation causes thevirtual object to be viewable in an altered location wherein the eye hasan altered gaze direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of examples wherein:

FIG. 1 is a block diagram showing a viewing device, according to anembodiment of the invention that displays rendered content to an eye ofa user;

FIG. 2A is a perspective view of an eye and an optical display of theviewing device, wherein the optical display is undeformed;

FIG. 2B is a view similar to FIG. 2A wherein the optical display isdeformed;

FIG. 3A is a perspective view illustrating how a location of a renderedobject is established;

FIGS. 3B and 3C are front views that illustrate how a rendered object ismoved;

FIG. 3D is a top plan view illustrating how a location of a renderedobject can be moved using different insertion angles that are providedby a laser projector;

FIG. 4 is a perspective view illustrating potential gaze vector errors;

FIGS. 5A to 5D illustrate a statistical approach for determining alikely location of a virtual object and incremental movement of thevirtual object to correct for its displacement;

FIGS. 6A to 6C illustrate movement of a virtual object due to displaydeformation and correction of movement of the virtual object;

FIGS. 7A to 7E illustrate movement of the virtual object due to displaydeformation with a corresponding change in gaze angle (FIGS. 7A to 7B),the effect of deformation of an eye tracking camera on a calculated gazeangle (FIGS. 7C and 7D), and correction of the gaze angle (FIG. 7E);

FIGS. 8A to 8D illustrate movement of a virtual object and acorresponding change in gaze vector (FIGS. 8A and 8B), and the effect ofdeformation of an eye tracking camera on a calculated gaze angle (FIGS.8C and 8D);

FIG. 9 illustrates one solution to rectify a resultant change in gazeangle as represented in FIG. 8D;

FIGS. 10A to 10C illustrate a different solution than FIG. 9 to rectifythe resultant gaze angle in FIG. 8D;

FIG. 11 is view similar to FIG. 1, further illustrating a referencesystem of the viewing device for purposes of integrating the processshown in FIGS. 10A to 10C;

FIG. 12 is a flow chart illustrating functioning of the viewing device;and

FIG. 13 is a block diagram of a machine in the form of a computer thatcan find application in the present invention system, in accordance withone embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 of the accompanying drawings illustrates a viewing device 20,according to an embodiment of the invention that is used to displayrendered content to an eye 22 of a user. The viewing device 20 includesa display assembly 24, a deformation detection system 26, a user inputdevice 28 and a correction system 30.

The display assembly 24 includes a video data receiver 32, a projector34 and an optical display 36 connected directly or indirectly to oneanother. The display assembly 24 includes a structure (not shown) thatis securable to a head of a user with the optical display 36 in front ofthe eye 22 of the user. The optical display 36 is a transparentcomponent that allows the eye 22 to see objects in the real world behindthe optical display 36 and can simultaneously project virtual images tothe user such that light associated with real and virtual objects isvisible to the user.

The video data receiver 32 is connected or connectable to a video datachannel which carries color and intensity values of pixels. Theprojector 34 has a laser and a scanner that are capable of creating atwo-dimensional pattern based on the video data. The optical display 36is located in a position for the laser of the projector 34 to couplelaser light into the optical display 36. The laser light then propagatesthrough the optical display 36 and exits the optical display 36 througha pupil of the optical display 36 towards the eye 22. The eye 22 thusreceives light from the real world objects behind the optical display 36and light that is generated by the projector 34. An augmented realityview is then created on a retina 38 of the eye 22, the augmented realityview including light from the real world scene visible to the userthrough the optical display 36 combined with light created by theprojector 34 that represents virtual content.

The deformation detection system 26 includes an attention generationunit 40, an input trigger 42, an eye tracking camera 44, a gaze anglecalculation module 46, a statistical system 48, and a correctioncalculation unit 50.

The attention generation unit 40 is connected to the video data receiver32. The attention generation unit 40 is configured to provide anoverride functionality to the video data receiver 32. The attentiongeneration unit 40 may for example insert a virtual object within thedata stream received by the video data receiver 32, change the color ofa virtual object and/or reduce the size of a virtual object for thepurpose of having the eye 22 direct its gaze angle towards the virtualobject and focus on the virtual object. While an attention generationunit 40 is described, virtual content that can be used as a basis forcalibrating an augmented reality system may generally be provided by arendering system or module.

The input trigger 42 is connected to the user input device 28 anddetects a user input through the user input device 28. The user inputdevice 28 may for example be one or more of a joy stick, a wand, acamera that tracks a body part of the user, a button, a touchpad, asensor-equipped glove, a mouse, a keyboard, etc. The user input device28 provides an input to the input trigger 42.

The eye tracking camera 44 is mounted to the display assembly 24 in aposition to capture an image of the eye 22. In some embodiments, one ormore camera per eye is used to image a user's eyes. Alternatively, asingle camera having a sufficiently wide angle to capture an imageincluding both of the user's eyes may be used.

The gaze angle calculation module 46 is connected to the eye trackingcamera 44 and the input trigger 42. The gaze angle calculation module 46calculates a gaze angle of the eye 22 based on an image captured by theeye tracking camera 44. The gaze angle calculation module 46 isconnected to the input trigger 42 and is activated by the input trigger42 such that a gaze angle is calculated by the gaze angle calculationmodule 46 when a user input is detected. While the system is describedusing a calculated gaze angle, any other eye gaze orientationcharacteristic may also be used such as, for example, a gaze vector, agaze coordinate, a visual axis orientation, or a cornea center location.Additionally, gaze data from the left and right eyes may be used incombination to gather information about the location on which a user'seyes are focused.

The statistical system 48 is connected to the gaze angle calculationmodule 46 and receives a large number of gaze angle calculationmeasurements. The statistical system 48 records a gaze angle receivedfrom the gaze angle calculation module 46 each time that the inputtrigger 42 activates the gaze angle calculation module 46. Thestatistical system 48 thus collects a number of gaze angles over aperiod of time. The statistical system 48 then calculates astatistically relevant gaze angle, for example a median gaze angle fromthe gaze angles that are recorded by the statistical system 48. Arepresentative gaze angle may be selected or calculated and may be usedin a comparison to an expected gaze angle associated with the displayingof virtual content. If the representative gaze angle is substantiallydifferent from the expected gaze angle, deformation within the system isconcluded to have occurred.

The correction calculation unit 50 is connected to the statisticalsystem 48. The correction calculation unit 50 calculates a desiredcorrection in the location of the rendered virtual object that iscreated or modified by the attention generation unit 40.

The correction system 30 is connected to the correction calculation unit50. The correction system 30 receives correction data from thecorrection calculation unit 50. The video data receiver 32 is connectedto the correction system 30. The correction system 30 modifies thelocation of the virtual object that is created or modified by theattention generation unit 40. The correction system 30 also modifies thelocations of all other objects in the video stream by the same amountand direction that the location of the virtual object generated andmodified by the attention generation unit 40 is corrected.

In use, the user attaches the viewing device 20 to their head with theoptical display 36 in front of the eye 22. The user can then see realworld objects through the transmissive optical display 36 and cansimultaneously view rendered virtual content.

The video data receiver 32 receives video data from a backgroundapplication. The background application may for example be a movieapplication for displaying a movie, a game, a web browser, a menu, alauncher, two-dimensional content, three-dimensional content or anyother type of virtual content. The video data includes data representingframes of images that are received at video data rates. The video dataincludes pixels with intensity and color values. The video data receiver32 provides the video data to the projector 34. The projector 34 createsa two-dimensional pattern for each frame. The pattern may include laserlight bundles, with each bundle representing a respective pixel, and itsintensity and color being modulated. The projector 34 couples thepattern into the optical display 36 either directly or indirectlythrough lenses, mirrors, gratings, or the like. The pattern transmitsthrough the optical display 36 and exits the optical display 36 towardsthe eye 22. The light beam 54 represents light that transmits from theoptical display 36 towards the eye 22. It should however be understoodthat many light beams representing a virtual object are projected fromthe optical display 36 such that the image received by the retina 38resembles the pattern created by the projector 34. In some embodimentsthe virtual object may be perceived by a user as being three-dimensionaldue to one or more wavefront shaping techniques applied to the lightrepresenting the virtual object. A dynamic image can be seen by the userin embodiments where the pattern continuously changes with each frame ofdata that is provided by the video data receiver 32 to the projector 34.

The video data that is received by the video data receiver 32 includesdata representing one or more objects that are to be displayed on theretina 38 of the eye 22. A virtual object that is represented in thedata received by the video data receiver 32 may actually be displayed onthe optical display 36. However, it is possible that such a virtualobject is not visible or easily discernible on a surface of the opticaldisplay 36 due to a number of factors including that the optical display36 is a see-through display and/or that the optical display 36 primarilyserves as a waveguide to direct light between the projector 34 and theeye 22. The video data provided by the video data receiver 32 to theprojector 34 still includes data representing objects even if thevirtual objects may not be visible on the surface of the optical display36. For purposes of discussion, it will be assumed that a virtual objector objects are visible on a surface of the optical display 36. It shouldhowever be understood that objects are shown on a surface of the opticaldisplay 36 for ease of illustration. The invention deals primarily witha calibration methodology that is the same whether objects are actuallyvisible or not visible on a surface of the optical display 36.

During normal operation of the viewing device, the attention generationunit 40 does not provide an override functionality to the normaloperation of the video data receiver 32. All video data is presented tothe user at a video refresh rate without any interference of thedeformation detection system 26. The deformation detection system 26only overrides the normal functionality of the video data receiver 32 afew times per day (e.g., 50 to 100 times per day of continued use) totake measurements while the video data receiver 32 proceedsuninterrupted for the remainder of the time. The user input device 28and the eye tracking camera 44 are connected to the backgroundapplication. During normal operation of the video data receiver 32, theuser may use the user input device 28 to provide instructions to thebackground application or to otherwise interact with virtual contentrendered on the optical display 36 while the one or more eye trackingcameras 44 continue to monitor the eyes 22. The user may for example usethe user input device 28 to interact with a virtual object that isdisplayed to the user via the optical display 36 while the backgroundapplication relies on the eye tracking camera 44 to know when the useris looking at the virtual object.

There is very little or no deformation of the display assembly 24following factory calibration of the viewing device 20. Objects that aredisplayed using the optical display 36 are in their expected locationsrelative to a gaze angle of the eye 22. Over time with use of theviewing device 20, components of the viewing device 20 including orconnected to the display assembly 24 begin to deform. The deformationmay manifest in a deformation of the optical display 36, deformation ofhinges and deformation of materials that are used in the structure thatmounts the viewing device 20 to the head of the user. The deformation isusually due to a combination of small or large stresses that are placedon the components of the display assembly 24 and the materials of thecomponents of the display assembly 24. Stresses may for example becreated when cabling that are connected to the optical display 36 pullon the optical display 36, when a user fits the viewing device 20 totheir head or removes it from their head and when the user operates thehinges, springs, or other dynamic components for purposes of unpackingor storing the viewing device 20. The material properties of thecomponents of the display assembly 24 may be subjected to fatigue whenstresses are cycled and it is known that plastics materials experience“creep” when subjected to stresses over time. Some materials of theviewing device 20 may also experience thermal loading, and such changesin temperature may contribute to deformation of one or more components.The result of the deformation is that the actual location at whichvirtual objects appear to the user on a deformed viewing device 20 isnot the intended rendering location of those virtual objects. As aresult, the actual gaze of the user is different from the gaze thatwould be expected if the user were to look at the rendered virtualcontent at its intended rendering location. In addition, deformation iscontinuous, so it is expected that the rendering location of virtualobjects as perceived by the user will continue to move over timerelative to the intended rendering location. The display assembly 24initially displays a virtual object in a select location wherein the eye22 has an expected gaze direction. The deformation of the displayassembly 24 causes the virtual object to be viewable in an alteredlocation wherein the eye 22 has an altered gaze direction.

One or more components of the deformation detection system 26 may befunctionally and structurally connected to the display assembly 24 todetect the deformation of the display assembly. The correction system 30is connected to the deformation detection system 26. The correctionsystem 30 displays, with the display assembly 24, the virtual object ina corrected location. When the virtual object is displayed in thecorrected location, the eye 22 viewing the virtual object in thecorrected location has a corrected gaze direction that is moved closerto the expected gaze direction than the altered gaze direction. Thedeformation detection system 26 provides an overriding or augmentationfunctionality to the normal operation of the viewing device 20 describedabove. The deformation detection system 26 is intermittently activated,for example 10 to 20 times per hour during continuous operation. Inaddition, the deformation detection system 26 is only activated for afew seconds, for example three to seven seconds, which is as long as isneeded to take measurements and make an adjustment. The viewing device20 operates normally during the remainder of the time.

The functioning of the deformation detection system 26 is initiated byactivating the attention generation unit 40 while the user input device28 is connected to the input trigger 42 and the eye tracking camera 44continues to monitor the eye 22. What is primarily required is for theuser to interact with a rendered object that is received by the videodata receiver 32 from the background application that is small enough tominimize gaze vector error. The attention generation unit 40 may alsomodify the color of the virtual object or reduce its size to grab theuser's attention and help draw the eye 22 to a small point where thevirtual object is located. The video data receiver 32 provides datarepresenting the virtual object to the projector 34. The projector 34then generates light and projects the light representing the virtualobject toward the optical display 36 for viewing by the user.

The virtual object that is being placed or modified by the attentiongeneration unit 40 is of the kind that requires that the user interactwith the rendered virtual object using the user input device 28. Such avirtual object may for example be a play button, a target, anapplication launching icon, etc. When the user uses the user inputdevice 28 to interact with the rendered virtual object, the eye 22 ofthe user is assumed to be looking at that rendered virtual object on theoptical display 36. The eye tracking camera 44 captures an image of theeyes 22 and provides the image data to the gaze angle calculation module46. The user input device 28 activates the input trigger 42, whichinstructs the gaze angle calculation module 46 to calculate a gaze angleof the eye 22 using the data received from the eye tracking camera 44.The gaze angle that is calculated by the gaze angle calculation module46 is representative of an actual location of the rendered virtualobject on the optical display 36 as perceived by the user.

The gaze angle calculation module 46 provides the gaze angle to thestatistical system 48. The statistical system 48 stores the gaze angle.When the deformation detection system 26 is activated a second time, theprocess is repeated and the statistical system 48 stores a second gazeangle. The process is repeated until the statistical system 48 hasstored enough gaze angles to allow the statistical system 48 tocalculate a statistically relevant altered gaze angle. The statisticalsystem 48 may for example calculate an average, a mean or a median gazeangle from the collected gaze angles. The statistical system maycalculate a statistically relevant gaze angle from all the measurements,although it is preferably that the statistical system only uses gazeangles that are outside a predetermined error range (e.g., 90arcminutes) as data points for calculating a statistically relevant gazeangle. Alternatively, in some embodiments, rather than accumulatingmultiple measurements to calculate a statistically determined gaze anglebefore performing an incremental correction, each measured gaze anglethat is determined to lie outside of a tolerance error of the expectedgaze angle may result in an incremental correction to the renderinglocation of virtual content.

The statistical system 48 provides the altered gaze angle to thecorrection calculation unit 50. The correction calculation unit 50determines the amount of correction that is needed in the gaze angle toreturn the gaze angle from the altered gaze angle back to the expectedgaze angle. The correction calculation unit 50 calculates both thedirection and the amount of correction that is required and thencalculates an actual correction that is only a small fragment of therequired correction. The correction calculation unit 50 then providesthe actual correction to the correction system 30. The correction system30 provides the correction to the video data receiver 32. The video datareceiver 32 then moves the virtual object generated by the attentiongeneration unit 40 and all other objects in accordance with thedirection and magnitude of the actual correction received from thecorrection system 30.

The statistical system 48 may require a large number of measurements,for example 50 to 100 measurements, before providing an altered gazeangle to the correction calculation unit 50. In addition, any correctionthat is made is only a small fraction of the actual change in the gazeangle due to the deformation of the display assembly 24. The cumulativecorrection is thus a slow process. By way of example, only a singlecorrection may be made during continuous operation of eight hours in oneday and it may take several days or weeks for the gaze angle to becorrected within tolerance of the expected gaze angle. Alternatively,several small corrections may be made during use of the device. Thenumber of corrections may depend on how many times a user interacts withvirtual content that is considered to be reliable for gaze anglecalculation and rendering location calibration. Such a slow processallows for recalculation in case that a mistake is made and allows forcontinued acceleration and deceleration of the deformation of thedisplay assembly 24 with less risk of over shooting the requiredcorrection that has to be made given continued deformation of thedisplay assembly 24.

In FIG. 2A the undeformed shape 60 represents the optical display 36before deformation. A rendered object 62 is placed in the opticaldisplay 36 to attract the attention of the user. When the user looks atthe rendered object 62, an actual gaze vector 64 can be defined. Theactual gaze vector 64 is a direction or axis along which the eye 22 isdirected for purposes of viewing a virtual object. The actual gazevector extends from a center point 22 of the eye 22 through a center ofa pupil of the eye. In order to calculate the actual gaze vector 64, oneapproach would be to first calculate the actual center point 22 of theeye 22. It may also be possible to calculate the actual gaze vector 64without calculating the actual center point 22 of the eye 22, butinstead to use other anatomical information of the eye for that purpose.The expected gaze vector 64 extends through the optical display 36 andthe user perceives the rendered object 62 as an augmented object 68. Theaugmented object 68 is located in a plane that is represented by anundeformed shape 70. Because the plane of the undeformed shape 70 isfarther than a plane of the optical display 36, the user perceives theaugmented object 68 to be larger than the rendered object 62 and a fielddefined by the undeformed shape 70 to be larger than a field defined bythe undeformed shape 60. The user also perceives a table 72. Theperception that the user has is that of the table 72 augmented withrendered virtual content represented in FIG. 2A by the augmented object68.

Multiple infrared light emitting diodes (LED's) 74 may be included inthe eye tracking system. Each LED 74 transmits infrared light that formsa respective infrared spot (a “glint”) 76 on a surface of the eye 22.Reference number 78 represents infrared light that reflects from thespot 76 towards the eye tracking camera 44. The eye tracking camera 44captures the locations of all of the spots created by the LED's 74 onthe surface of the eye 22. The locations of the spots 76 are used by thegaze angle calculation module 46 to calculate the gaze angle or gazevector of the eye 22. In some embodiments, eye tracking cameras may alsocapture a location of a pupil. Pupil location data can be used incombination with infrared glints to determine an eye position. A gazeangle or gaze vector may be calculated or otherwise determined based onthe eye position information.

The expected gaze vector 64 is shown in FIG. 2A passing through a centerof rendered object 62 and augmented object 68. Reference number 82represents light reflecting from the eye 22 that is captured by the eyetracking camera 44. In some embodiments, the eye tracking camera 44 thuscaptures an orientation of the eye and the location of the pupil 80. Thegaze angle calculation module 46 calculates the actual gaze vector(which in FIG. 2A is coincident to the expected gaze vector 64) using atleast the location of the interactable rendered virtual content. In someembodiments, the location of the eye 22 with respect to the opticaldisplay 36 may also be used.

It may not always be necessary to take measurement for purposes ofdetermining a pre-deformation gaze angle. For example, when the viewingdevice 20 is new, it can be assumed that the display assembly 24 isundeformed and that the gaze angle of the eye 22 is as represented bythe expected gaze vector 64 when the rendered object 62 is located asshown. The rendered object 62 can thus be located as shown and theexpected initial gaze vector 64 can be determined without any additionalmeasurements. The expected and actual gaze angles will change based onlocation of the rendered content. While an “initial” gaze angle or“pre-deformation” gaze angle could be calculated, an expected gazevector can be assumed from the background application or from a previouscalculation. A difference can then be calculated between the assumedexpected gaze angle and actual gaze angle that is newly beingcalculated.

In FIG. 2B, the shape 86 represents deformation of the optical display36. The deformation of the optical display 36 is represented by thedifference in the shape 86 when compared to the undeformed shape 60. Therendered object 62 is still rendered in the same (x, y) location on thedisplay but deformation of the display with respect to the user has theuser perceive the content at a location different from the intendedlocation. Due to the deformation, the rendered object 62 is no longer inthe location shown in FIG. 2A, but it has moved by a distance and adirection as represented by the vector 88. The rendered object 62 hasthus moved in a direction that is a result of the deformation of theoptical display 36 in the area of the rendered object 62. An alteredgaze vector 90 is defined between the eye 22 and the rendered object 62.The user views the rendered object 62 as an augmented object 68 within aplane as represented by the shape 92. The shape 92 is deformed relativeto the undeformed shape 70 in a manner similar to the deformationbetween the shape 86 and the undeformed shape 60.

When the user looks at the augmented object 68, the actual gaze vector90 passes from the eye 22 to the location of the augmented object 68 inthe deformed shape 92. In this example, the actual gaze vector 90 isdifferent from the expected gaze vector 64. The eye tracking camera 44continues to capture eye location information, which may be based onpupil location within images and/or glint reflection patterns, so thatthe gaze angle calculation module 46 can calculate the actual gazevector 90 and compare it to the expected gaze vector 64 to infer whetherdisplay assembly deformation has occurred.

FIG. 3A illustrates how the location of the rendered object 62 iscorrected. The projector 34 projects image light 94 associated with avirtual image or object at a predetermined angle toward the opticaldisplay 36. The image light 94 may encounter one or more diffractiveoptical elements, such as an incoupling grating 95, an orthogonal pupilexpander 97, and an exit pupil expander 99, disposed in or on awaveguide 101 as part of the optical display 36. As the image light 94propagates through the waveguide 101, the diffractive optical elementsredirect the light in different ways, ultimately resulting in the imagelight 94 exiting the waveguide through the exit pupil expander 99 towardthe user's eyes 22. The user's eye 22 can focus image light 94 at alocation on the retina for the user to perceive the rendered object 62.

Referring to FIGS. 3B and 3C, two examples of images projected as imagelight 94 are shown. In FIG. 3B, virtual content object 115 is shown inthe center of the image 94 a. When image 94 a is projected toward anundeformed optical display 36 and travels through the componentsthereof, the user will see virtual content object 115 centered in thefield of view. However, if image 94 a is projected toward a deformeddisplay, the virtual content object 115 may be perceived by the user tohave shifted to the right, for example, such that it is no longercentered in the field of view. To correct for the shift caused bydeformation and detected by comparing expected and actual gaze vectors,the image 94 b may be projected instead of image 94 a. In image 94 b,the virtual content object 115 is shifted toward the left of the imagesuch that when the light exits the deformed display at a rightwardshift, the display's right shift cancels out the content's left shiftand the virtual content object 115 appears to the user to be centered inthe field of view. The pixel shifting may be accomplished by lighting updifferent pixels of a spatial light modulator (SLM) within the projector34 using LED or other similar light sources. In such an adjustmentmethod, it may be useful to convert the actual and expected gaze anglesor gaze vectors into a display coordinate system. For example, thesystem may expect for a user's gaze to center on pixels at coordinates(x1, y1) but finds that the user's gaze is actually centered on pixelsat coordinates (x2, y2) in the display coordinate system. In such amethod, pixel shifting can be adjusted by an amount equal and oppositeto the difference between the expected viewing coordinates and theactual viewing coordinates as determined by the user's gaze vector.Alternative means for adjusting the rendering location of virtualcontent may also be used.

In some embodiments, as shown in FIG. 3D, correction may be accomplishedby adjusting the projector 34 itself. For a complete correction, therendering location of the rendered object 62 has to move from thelocation 100 in a direction represented by a vector 102 to a correctedlocation 104. For a complete correction, the projector 34 may insertlight 106 at an adjusted angle into the diffractive optical elements ofthe optical display 36 so that the rendered object 62 is viewable nearerto an intended location within the field of view. The user will perceivethe rendered object 62 to have moved from the location 100 along vector102 toward the location 104. However, a complete correction is not made.Instead, the rendered object 62 is moved by a small fraction of thedistance between location 100 and location 104 along the directionrepresented by the vector 102. The projector 34, for purposes of makinga partial correction, thus inserts light at an angle that is slightlysteeper than the image light 94, but not as steep as the light 106.

FIG. 4 illustrates potential gaze vector errors 120 and 122 at two userinteraction events. Anatomically an eye is continually moving when it isfocused on a static image, such as the augmented object 68. Natural eyemovement typically results in about 60 arcminutes of error or deviationfrom a central gaze vector corresponding to the direct path from aselected anatomical marker of the eye, for example the center point 66of the eye 22, to augmented object 68. In some embodiments, the gazevector may be defined as a direct path from the center of a cornea of aneye to the augmented object 68, or may be defined as the extension ofthe visual axis of the eye. If the user looks at the augmented object68, gaze vectors within an expected gaze vector range having a 60arcminute radius from the gaze vector 90 may considered to be directedtoward the location of augmented object 68. The gaze angle calculationmodule 46 in FIG. 1 may also have some error for given eye sizes,shapes, etc. and such an additional error can add, for example, around30 arcminutes to the expected gaze vector range radius. When it isdetermined that the user is looking at the augmented object 68 and agaze vector that is calculated is within a 90 arcminute radius of thegaze vector 90, the system is considered to be well calibrated.

One challenge is that the relatively large 90 arcminute radius of errorin gaze vector makes it difficult to determine the exact location of theactual perceived position of the augmented object 68. In order toaccount for potential errors, the statistical system 48 in FIG. 1 maycollect multiple data points to discover trends. The trends in thedetermined gaze vectors are accumulated to discover the likely locationof the actual perceived position of the augmented object 68 as displayedby a system having some amount of deformation. Because it is stilluncertain how much of the position discrepancy is noise due to eyemotion or algorithm errors and how much is due to actual deformation ofthe display assembly 24 in FIG. 1, a complete correction of the gazevector is not carried out. By way of example, correction increments canbe between 0.01 to 0.5 arcminutes, for example 0.1 arcminutes.Alternatively, the correction increment amount can be based on theamount of deformation detected, with a larger deformation necessitatinglarger increments. By way of example, the correction increments may betwo orders of magnitude smaller than the detected deformation amount.

FIGS. 5A to 5D illustrate one of many scenarios that may unfold. In FIG.5A, a number of gaze vector measurements are taken that point tolocations 124A to 124C. The empty circles of locations 124A to 124Crepresent measured gaze angles that have been calculated. The darkcircle of the location 126 indicates it is the location where the systemexpected the virtual object to be. The measured gaze vectors locations124A to 124C are used by the system to calculate a statisticallyrelevant location 130 of where the virtual object is now likely to belocated. The measured gaze vectors at locations 124A to 124C indicatethat a virtual object may have moved from an initial expected location126 in a direction as represented by a vector 128 to a statisticallydetermined altered location 130. In FIG. 5B, the virtual objectrendering position is moved in a direction represented by a vector 132which is opposite to the direction represented by a vector 128 andsmaller in magnitude. The assumption is that the virtual object waslocated at the location 130 and has been moved to a new location 134along a direction of the vector 132 toward the expected renderinglocation 126.

In FIG. 5C, further data points 124D to 124G are collected thatstatistically determine that the virtual object is located at an alteredlocation 136. The location 136 is on an opposite side of the location126 than the location 130. The change in object location may be a resultof continued deformation of the display system. It is also possible thatan error was made due to noisey data in FIG. 5A when determining thatthe virtual object was at the location 130 and/or that the virtualobject has moved in an opposite direction. When adjusting the renderinglocation by the vector 132 as shown in FIG. 5B, if the virtual objectwas actually perceived to be in location 136 as shown in FIG. 5C, it canbe seen that it is possible that through an incorrect recalibration inFIG. 5B, the virtual object may have been moved to a new location 138.The location of the vector 132 in FIG. 5B thus represents how the system“believed” it was moving the virtual object at the time of FIG. 5B,although it can now be seen that the vector 132 is in a differentlocation in FIG. 5C to represent how the virtual object was more likelymoved at the time of FIG. 5B now that more data is available forpurposes of analyzing the location of the virtual object. The vector 132has the same magnitude and direction in FIGS. 5B and 5C. The onlydifference in the vector 132 between FIGS. 5B and 5C is that thelocation of the vector 132 is different, with the location of the vector132 in FIG. 5B representing how the system believed it was moving thevirtual object and the location of the vector 132 in FIG. 5Crepresenting what had likely happened when the virtual object was movedin FIG. 5C. In FIG. 5C it can be seen that the movement of the virtualobject from the location 136 in the direction represented by a vector132 to the location 138, which can be traced back to FIG. 5B, was anerror because the virtual object was moved further from the expectedlocation 126 instead of nearer to it. In such an example, it isadvantageous that incremental adjustments are made rather than completeadjustments.

In FIG. 5D, further data points 124H to 124L are collected whichindicate that the virtual object is likely at a new location 140. Thevector 132 is in its same location in FIG. 5D as in FIG. 5C to representthe error that was made at the time of FIG. 5B. The location 140 haspassed the location 138 and the mistake that was made by moving thevirtual object in the direction represented by a vector 132 to thelocation 138 has thus been eviscerated.

FIGS. 5A to 5D do not illustrate every possible scenario that mayunfold, but merely serve to illustrate that by moving the virtual objectin small increments as opposed to a single large movement that attemptsto correct for all the movement of the virtual object due to thedeformation of the display assembly 24, incorrect adjustments that couldbe made based on noisy data are prevented from being noticeable to auser.

FIG. 6A illustrates a view as seen by the user, including a real worldtable 72 and a rendered object in the form of a coffee mug, which mayfor example be the augmented object 68 in the planes of the shapes 70and 92 in FIG. 2B. The coffee mug has been moved in the view of the useras represented by the vector 150. The designation “Display” at thevector 150 indicates that undeformed shape the movement of the virtualobject, as shown by the vector 150, is due to deformation of the displayassembly 24 in FIG. 1.

FIG. 6B illustrates the movement of the gaze angle as calculated by thegaze angle calculation module 46 in FIG. 1 based on the view of the eyetracking camera 44 in FIG. 1. The deformation of the display assembly 24in FIG. 1 results in movement of the gaze angle as measured by the eyetracking camera 44 in the direction indicated by the vector 152. Thevectors 150 and 152 in FIGS. 6A and 6B are equal to one another. Themovement in the gaze angle that is calculated in FIG. 6B is thus thesame as the movement of the virtual object within the vision of the useras shown in FIG. 6A, subject to the tolerances of the eye and thetracking algorithms as described with reference to FIG. 4.

In FIG. 6C, the virtual object is incrementally moved in a directionthat is shown by the vectors 154. The vectors 154 are in a directionopposite to the vector 152, but each vector is only a fraction of thelength of the vector 152. The sum of the vectors 154 equals the vector152 except in an opposite direction. If the virtual object is moved bythe entire distance of all the vectors 154, the virtual object is, overtime, returned to its position before the deformation of the displayassembly 24 as shown in FIG. 6A, and earlier movement of the virtualobject due to display deformation is accounted for.

FIGS. 6A to 6C illustrate the scenario where there is no deformation ofthe eye tracking camera 44 in FIG. 1. Because there is no deformation ofthe eye tracking camera 44, measurements taken by the eye trackingcamera 44 result in measurements of gaze angles that match the actualgaze angles of the eye 22 of the user with respect to the display,subject to the tolerances discussed above.

FIGS. 7A to 7E collectively illustrate an effect that deformation of theeye tracking camera 44 in FIG. 1 can have in combination withdeformation of the display. FIG. 7A illustrates the movement of thevirtual object within the view of the user due to the deformation of thedisplay assembly 24 in FIG. 1 if deformation of the camera is not takeninto consideration. FIG. 7A is thus the same as FIG. 6A. It should benoted that the any deformation of the eye tracking camera 44 does notaffect the positioning of the virtual object within the vision of theuser as illustrated in FIG. 7A, but affects the gaze vector that iscalculated with respect to the display. Therefore, even if there is alsocamera deformation and the effect of camera deformation is taken intoconsideration, FIG. 7A will still represent movement of the virtualobject within the vision of the user.

FIG. 7B illustrates the movement of the gaze angle as calculated by thegaze angle calculation module 46 in FIG. 1 based on image data receivedfrom the eye tracking camera 44 if, as with FIG. 7A we do not take theeffect of camera deformation into consideration. FIG. 7B, thus assumesno deformation of the eye tracking camera 44 and is therefore the sameas FIG. 6B.

FIG. 7C illustrates the effect of the calculated gaze angle when we takethe effect of deformation of the eye tracking camera 44 intoconsideration but without the effect of deformation of the display.Referring to FIG. 2A, deformation of the eye tracking camera 44 causeserror in the position measurement of the eye 22 within the view of theeye tracking camera 44. Such error in the eye tracking camera 44 causesa change in the image data that the eye tracking camera 44 provides tothe gaze angle calculation module 46 in FIG. 1. The gaze angle that iscalculated by the gaze angle calculation module 46 is thus affected bythe deformation of the eye tracking camera 44. FIG. 7C illustratesmovement of the gaze angle that is calculated due to deformation of theeye tracking camera 44 and is represented by the vector 156. The errorin gaze angle accuracy with respect to the display that is caused bycamera deformation is usually relatively small. The movement in the gazeangle due to camera deformation is typically on the order of about 1/20of the movement in the gaze angle due to display deformation.

FIG. 7D illustrates a resultant 158 of the vectors 152 and 156. In thepresent example, the vector 156 representing the effect of the cameradeformation is at an angle of less than 90° of the vector 152representing the display deformation. The vector of the resultant 158 istherefore longer than the vector 152 representing the effect of thedisplay deformation.

In FIG. 7E, the virtual object is moved within the vision of the user asrepresented by the vectors 160. Each vector 160 is in a direction thatis opposite to the resultant 58 in FIG. 7D. The virtual object is movedin increments each time the user interacts with an eligible virtualobject. Over a period of days or weeks, the correction vectors 160 addup to the resultant 158 within the anatomical eye tolerance plus anytolerance required by tracking algorithms. As noted before, the effectof the camera deformation is relatively small. The virtual object isthus moved from a location that is closer to its location shown in FIG.7A than in its location shown in FIG. 7E. In the case of the virtualcoffee mug which is intended to appear to the user to be sitting on thetable 72, the coffee mug will thus return to the top of a table or veryclose to the top of the table.

FIGS. 8A and 8B are similar to FIGS. 7A and 7B. In FIG. 8C, the effectof camera deformation results in a movement of the gaze angle asrepresented by the vector 164. An angle between the vector 164 and thevector 152 is more than 90°.

FIG. 8D illustrates a resultant vector 166. The resultant vector 166represents the calculated change in the gaze angle due to the displaydeformation and the camera deformation. The resultant vector 166 issmaller than the vector 152 representing the effect of the displaydeformation. The effect of the display deformation and the cameradeformation can be said to be in “opposite” directions in FIG. 8D and inthe “same” directions in FIG. 7D.

FIG. 9 illustrates one possible solution when the effect of the displaydeformation and the effect of the camera deformation are in oppositedirections on the calculated gaze angle. The correction system 30 inFIG. 1 does not modify the positioning of the virtual object. The usermay, for example, not care whether a “play” button is located on a tableor floating at some distance above the table. In addition, the playbutton should function properly as an interface element for thebackground application.

FIGS. 10A to 10C illustrate a solution as an alternative to the solutionin FIG. 9. In FIG. 10A, the gaze angle change due to deformation of thecamera is calculated starting when the viewing device is still new, alsoreferred to as the “out-of-box” condition. The change in a calculatedeye position with respect to the eye tracking camera due to cameradeformation is periodically determined using the eye tracking camera 44and data analysis of the generated eye tracking images. The methodologyfor calculating an eye position or eye center at any particular time issimilar to the methodology described with reference to FIG. 2A. Imagesof the eyes 22 continue to serve as a basis for calculating eye centerpositions of each eye with respect to the one or more eye trackingcameras. Change in the eye center positions within collected imageframes can be attributed to changes in location of the eye trackingcameras with respect to the eyes. While there is some error associatedwith device fit and consistency of how the user dons the device, the useof multiple image frames in the data analysis improves accuracy ofdetermining eye tracking camera deformations. For example, the eyecenter calculated from eye tracking images taken during a setup phase ofthe device is determined to be at some coordinate location (x, y, z).Over time, eye tracking camera deformation could occur such that thecamera tilts slightly downward. The position of the eye in the imagescaptured with the deformed eye tracking camera will change such that theeye center is shown to be at a higher y-axis location, for example at acoordinate location (x, y+1, z) within the eye tracking image. Thechange between the two coordinate locations is linked to the change inthe eye tracking camera and that difference can be used to correct arendering location of virtual content on the display. The eye trackingcamera deformation is represented in FIG. 10A as vector 170 and canoccur in one, two, or three dimensions.

The eye tracking camera 44 runs continuously, for example at a rate of30 frames per second. In determining the deformation of the eye trackingcamera 44, it is not necessary to wait for the user to interact withparticular virtual content renderings for data collection to take place.A stream of image data may be available for comparison to baseline atany given time. The use of a set of data points from the eye trackingcamera 44 to compare against the baseline data provides for a robustsystem. For example, the use of at least the last 10 images from the eyetracking camera 44 can improve accuracy over the use of only one or twoimages.

FIG. 10B illustrates that the vector 166 is the sum of the vectors 152and 170. The vector 152 can be calculated by deducting the cameradeformation vector 170 from the vector 166. Because the vector 152represents the effect of the display deformation on the location of thevirtual object, the virtual object can be moved in direction opposite tothe vector 152.

In FIG. 10C, the virtual object is incrementally moved as represented bythe vectors 172. A sum of the vectors 172 is equal to the vector 152,but in an opposite direction.

As shown in FIG. 11, the viewing device 20 may further include areference system 180 for purposes of the making the calculations asshown in FIGS. 10A to 10C. The reference system 180 may include manybaseline calculations, images, and/or measurements such asinter-pupillary distance, eye center location, device fit information,eye shape information, visual axis location, and so on. The referencesystem 180 includes an out-of-box reference gaze angle 182 that iscalculated when the viewing device 20 is still new. The out-of-boxreference gaze angle 182 is stored in memory. The reference system 180further has an updated gaze angle 184 stored in memory. The updated gazeangle 184 is calculated on a periodic basis and represents the gazeangle that is most recently calculated. The reference system 180 furtherincludes a change 186 in a gaze angle due to camera deformation. Thechange 186 is a difference between the updated gaze angle 184 and theout-of-box reference gaze angle 182. The change 186 is represented inFIG. 10A by a sum of the vectors 170. The correction calculation unit 50functions to calculate the vector 152 in FIG. 10B. Other aspects of theviewing device 20 in FIG. 11 are the same as the viewing device in FIG.1 and similar reference numerals indicate similar components. While theout-of-box reference gaze angle is described as being a baseline forcomparison, any other eye characteristic, measurement, calculation, orimage may be used instead of, or in addition to, the out-of-boxreference gaze angle.

FIG. 12 illustrates the method as hereinbefore described. At 200, avirtual object is displayed at a select location wherein an eye viewingthe virtual object has an expected gaze direction. At 202, an expectedgaze vector range is determined based on the select location. At 204, auser interaction event is detected wherein the user interacts with thevirtual object. At 206, light reflected from an eye is captured with aneye tracking camera. At 208, an altered gaze vector is calculated basedon the light captured by the eye tracking camera. At 210, a comparisonis made between the determined altered gaze vector and the expected gazevector range. Elements 200 to 210 can be grouped into element 212,namely for detecting a deformation of the display assembly, wherein thedeformation causes the virtual object to be viewable in an alteredlocation wherein the eye has an altered gaze direction. It may bepossible to carry out element 212 without the specific elements listedas elements 200 to 210. Furthermore, although gaze vectors arecalculated, it may be possible to determine a gaze direction using amethod other than one that requires a calculation of a gaze vector.

At 214, a determination is made whether the actual gaze vector isoutside the gaze vector range. If the determination at 214 is negative,the process returns to 200. If the determination at 214 is positive, avirtual content rendering location correction amount and directionamount are calculated. At 220, the virtual content render location isadjusted by the calculated correction amount and direction. Elements 218and 220 can be grouped into element 222, namely for the display of thevirtual object in a corrected location wherein the eye viewing thevirtual object in the corrected location has a corrected gaze directionthat is moved closer to the expected gaze direction than the alteredgaze direction.

FIG. 13 shows a diagrammatic representation of a machine in theexemplary form of a computer system 900 within which a set ofinstructions, for causing the machine to perform any one or more of themethodologies discussed herein, may be executed. In alternativeembodiments, the machine operates as a standalone device or may beconnected (e.g., networked) to other machines. Further, while only asingle machine is illustrated, the term “machine” shall also be taken toinclude any collection of machines that individually or jointly executea set (or multiple sets) of instructions to perform any one or more ofthe methodologies discussed herein.

The exemplary computer system 900 includes a processor 902 (e.g., acentral processing unit (CPU), a graphics processing unit (GPU) orboth), a main memory 904 (e.g., read only memory (ROM), flash memory,dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM) orRambus DRAM (RDRAM), etc.), and a static memory 906 (e.g., flash memory,static random access memory (SRAM), etc.), which communicate with eachother via a bus 908 and a laser driver chip 12 or other light sourcedriver.

The computer system 900 may further include a disk drive unit 916, and anetwork interface device 920.

The disk drive unit 916 includes a machine-readable medium 922 on whichis stored one or more sets of instructions 924 (e.g., software)embodying any one or more of the methodologies or functions describedherein. The software may also reside, completely or at least partially,within the main memory 904 and/or within the processor 902 duringexecution thereof by the computer system 900, the main memory 904 andthe processor 902 also constituting machine-readable media.

The software may further be transmitted or received over a network 928via the network interface device 920.

While the machine-readable medium 924 is shown in an exemplaryembodiment to be a single medium, the term “machine-readable medium”should be taken to include a single medium or multiple media (e.g., acentralized or distributed database, and/or associated caches andservers) that store the one or more sets of instructions. The term“machine-readable medium” shall also be taken to include any medium thatis capable of storing, encoding, or carrying a set of instructions forexecution by the machine and that cause the machine to perform any oneor more of the methodologies of the present invention. The term“machine-readable medium” shall accordingly be taken to include, but notbe limited to, solid-state memories, optical and magnetic media, andcarrier wave signals.

The laser driver chip 12 includes a data store 161 and its own processor162. The data store 161 is used to store instruction and data structuresthat are specific to the operation of a laser source. The processor 162retrieves the instructions from the data store and has access to thedata structures to execute routines that drive the laser source so thatthe laser source generates laser light. The laser source forms part of aprojector that receives data such as video data. A scanner forms part ofthe projector to allow the projector to display the laser light over atwo-dimensional area, and in some instances in three-dimensional spacewith any patterns, color, saturation and other light qualities that arecreated by the projector being based on values in the video data.

Although a laser source and a laser driver chip 12 have been illustratedand discussed, it may be possible to use other display systems. Otherdisplay systems may for example include displays that make use oflight-emitting diode (LED) technology, organic light-emitting diode(OLED) technology, superluminescent light-emitting diode (SLED), or thelike.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative and not restrictive of the current invention, andthat this invention is not restricted to the specific constructions andarrangements shown and described since modifications may occur to thoseordinarily skilled in the art.

What is claimed:
 1. A viewing device for displaying rendered contentcomprising: a display assembly configured to display a virtual object ina select location on the display assembly, wherein an eye viewing thevirtual object has an expected gaze direction; and a deformationdetection system connected to the display assembly and configured todetect a measured gaze direction of the eye viewing the virtual objecton the display assembly and calculate a deformation of the displayassembly based on the measured gaze direction being an altered gazedirection that is different from the expected gaze direction.
 2. Thesystem of claim 1, further comprising: a correction system connected tothe deformation detection system to display, with the display assembly,the virtual object in a corrected location wherein the measured gazedirection of the eye viewing the virtual object in the correctedlocation is a corrected gaze direction, wherein a difference between theexpected gaze direction and the corrected gaze direction is less than adifference between the expected gaze direction and the altered gazedirection.
 3. The system of claim 1, wherein the display assemblyincludes: an optical display, the deformation being a deformation of theoptical display.
 4. The system of claim 3, wherein the optical displayis deformed in a display deformation direction and the altered gazedirection is moved relative to the expected gaze direction in thedisplay deformation direction.
 5. The system of claim 4, wherein theoptical display is transparent and the virtual object is viewable by theeye at a location on a side of the optical display opposing the eye. 6.The system of claim 3, wherein the deformation detection systemincludes: an eye tracking camera configured to capture light reflectedfrom the eye; and a gaze angle calculation module configured tocalculate the measured gaze direction of the eye based on the lightcaptured by the eye tracking camera.
 7. The system of claim 6, whereinthe measured gaze direction that is calculated by the gaze anglecalculation module is the altered gaze direction due to deformation ofat least one of the eye tracking camera and the optical display.
 8. Thesystem of claim 7, wherein: the difference between the expected gazedirection and the altered gaze direction is in a first direction and thechange in the measured gaze direction due to the deformation of the eyetracking camera is in a second direction and the first and seconddirections are less than 90 degrees relative to one another, furthercomprising: a correction system connected to the deformation detectionsystem to display, with the display assembly, the virtual object in acorrected location wherein the eye viewing the virtual object in thecorrected location has a corrected gaze direction that is moved towardthe expected gaze direction from the altered gaze direction.
 9. Thesystem of claim 7, wherein: the change from the expected gaze directionto the altered gaze direction is in a first direction and the change inthe measured gaze direction due to the deformation of the eye trackingcamera is in a second direction and the first and second directions areseparated by more than 90 degrees relative to one another.
 10. Thesystem of claim 9, further comprising: a correction system connected tothe deformation detection system to display, with the display assembly,the virtual object without moving the virtual object from the alteredlocation.
 11. The system of claim 9, further comprising: a correctionsystem connected to the deformation detection system to display, withthe display assembly, the virtual object in a corrected location whereinthe eye viewing the virtual object in the corrected location has ameasured gaze direction that is a corrected gaze direction, wherein thecorrected gaze direction is moved toward the expected gaze directionfrom the altered gaze direction.
 12. The system of claim 11, furthercomprising: a reference system to detect a change in the measured gazedirection due to the deformation of the eye tracking camera; acorrection calculation unit to determine the change in the measured gazedirection due to the deformation of the display assembly by deductingchange in the measured gaze direction due to the deformation of the eyetracking camera from the change in the gaze angle that is detected bythe deformation detection system; and a correction system connected tothe deformation detection system to display, with the display assembly,the virtual object in a corrected location wherein the eye viewing thevirtual object in the corrected location has a corrected gaze directionthat is moved in a direction opposite to the change in the gaze angledue to the deformation of the display assembly.
 13. The system of claim1, wherein the deformation detection system includes: a statisticalsystem configured to receive and analyze multiple measured gazedirection measurements; a gaze angle calculation unit that calculatesmultiple gaze directions, each gaze direction for a respectivemeasurement; and a correction calculation unit that determines thealtered gaze direction based on the multiple actual gaze directionmeasurements.
 14. The system of claim 1, wherein the deformationdetection system includes an attention generation unit configured toalter the display of the virtual object and attract a user's attentionto the virtual object before detecting the deformation.
 15. The systemof claim 14, wherein the attention generation unit is configured toattract the user's attention by changing a color of the virtual object.16. The system of claim 14, wherein the attention generation unit isconfigured to attract the user's attention to the virtual object byreducing a size of the virtual object.
 17. A method of displayingrendered content comprising: displaying, with a display assembly, avirtual object in a select location on the display assembly wherein aneye viewing the virtual object has an expected gaze direction; anddetecting a deformation of the display assembly, wherein the deformationcauses the virtual object to be viewable in an altered location whereinthe eye has an altered gaze direction.
 18. The method of claim 17,further comprising: displaying, with a display assembly, the virtualobject in a corrected location wherein the eye viewing the virtualobject in the corrected location has a corrected gaze direction that ismoved toward the expected gaze direction from the altered gazedirection.